Background: This is my Murray 38702X8A (38", dual blades, 12 hp B&S, bought new in early 1993). My regular repair/maintenance guy died a few years ago, so I've been handling everything myself since then. The mower has been generally rock solid since new, requiring only regular maintenance and a replaced front axle assembly 15 years ago -- caught the left front wheel on a low wall, bent up the axle pretty good, replaced the crappy original with an HD unit.
Doing PM a few weeks ago, I discovered worn spindle bearings. Bought all new parts including complete bearing assemblies, spindles, and bolts. Also bought fresh blades. I've swapped old for new, reattached the deck, and now she vibrates like a paint shaker when I engage the blades. This is not the normal vibration that occurs when blades are first engaged and settles out after a few seconds. This is pretty amazing -- I can see the deck vibrating through about 1/4 inch of travel. Vibration persists through all throttle settings. Mower is very smooth with engine running with blades disengaged. Engine crank and pulley spin true.
Here's what I've done so far to diagnose:
- Checked to be sure all the deck attachment points are properly pinned in place.
- Checked for tightness of the bearing assembly bolts.
- Removed the blades, checked balance (both good), and reinstalled, being sure they were centered properly, holes are proper size, blades not upside-down, and that all hardware was installed in proper orientation and tight.
- Spun the blades by hand to be sure they aren't bent or otherwise misaligned.
- Visually checked for runout of the spindles by spinning by hand. Also had the wife fire up the engine and engage the blades; watched for runout as they coasted down. Everything looks good.
- Checked spindle pulleys by the same methods. There is just enough of a wobble to be visible (less than 1/64"), but not enough to account for the violent shaking.
What am I missing? I'd hate to have to euthanize Ol' Red after 23 years of exemplary service (or suffer the shame of flat-bedding it to the local repair shop to expose my mistake).
Help, please. Thanks.
Burgess
Doing PM a few weeks ago, I discovered worn spindle bearings. Bought all new parts including complete bearing assemblies, spindles, and bolts. Also bought fresh blades. I've swapped old for new, reattached the deck, and now she vibrates like a paint shaker when I engage the blades. This is not the normal vibration that occurs when blades are first engaged and settles out after a few seconds. This is pretty amazing -- I can see the deck vibrating through about 1/4 inch of travel. Vibration persists through all throttle settings. Mower is very smooth with engine running with blades disengaged. Engine crank and pulley spin true.
Here's what I've done so far to diagnose:
- Checked to be sure all the deck attachment points are properly pinned in place.
- Checked for tightness of the bearing assembly bolts.
- Removed the blades, checked balance (both good), and reinstalled, being sure they were centered properly, holes are proper size, blades not upside-down, and that all hardware was installed in proper orientation and tight.
- Spun the blades by hand to be sure they aren't bent or otherwise misaligned.
- Visually checked for runout of the spindles by spinning by hand. Also had the wife fire up the engine and engage the blades; watched for runout as they coasted down. Everything looks good.
- Checked spindle pulleys by the same methods. There is just enough of a wobble to be visible (less than 1/64"), but not enough to account for the violent shaking.
What am I missing? I'd hate to have to euthanize Ol' Red after 23 years of exemplary service (or suffer the shame of flat-bedding it to the local repair shop to expose my mistake).
Help, please. Thanks.
Burgess